10 year old Grandee condensing oil boiler and Honeywell ST6400C - CH only works if HW set to on

[leooon]

Hi all,

I moved into my current house this year and since moving in the boiler has had a strange issue where I can only have the CH on if the HW is also set to on.

If I set CH to on, the boiler turns on but doesn't "ping" into action until I set HW on too; if I set HW on with CH off the rads warm up anyway. Is this an issue with the boiler or could it be an issue with the programmer? I don't have a room thermostat anywhere, just TRVs on every rad except the hall way one.

Also, if I turn HW on, should the boiler just idle until I turn a hot tap on somewhere?

I have had somebody round to look, but have asked him to give me a price for a service + potential parts, and also a price on a new boiler installed and am waiting for him to get back to me, but I think I'm looking at about 4k and I'd rather get a few more years out of this boiler if it's possible. This was also before I did any research on boilers and so I didn't really have a clue what he was talking about.

Thanks for any help.

 

[Agile]

It does not need a service but a diagnosis of the fault.

Did he not look at the motor valves and controls?

And talk to you?

Tony

 

[oilman]

Well we can't see the boiler from here, but it is likely to be the diverter valve and/or condensate dripping from the condenser onto the relay socket. A common problem with these boilers. Then again you don't say much about the boiler. Is it wall mounted, floor mounted , inside, outside?????

 

[leooon]

It does not need a service but a diagnosis of the fault.

Did he not look at the motor valves and controls?

And talk to you?

Tony

Hi,

He did, and he said he will go away and price up for the parts that could potentially need replacing, but I don't think he gave me a definite "this is the problem, this is what I need to fix it". He was the first person I've asked to have a look, so I'll probably try a couple others?

Well we can't see the boiler from here, but it is likely to be the diverter valve and/or condensate dripping from the condenser onto the relay socket. A common problem with these boilers. Then again you don't say much about the boiler. Is it wall mounted, floor mounted , inside, outside?????

Hi,

Sorry for lack of info. Its a wall mounted internal combi. He mentioned the diverter valve - but nothing about condensate dripping, what would this cause to happen/not happen?

Thanks.

 

[oilboffin]

Actuator sticking is what I'd look at.Bob

 

[oilhead]

Diverter valve actuator.

 

[oilman]

The condensate dripping is a design fault and occurs with the older version of the secondary heat exchanger.